dla_lin_berr.f (3)  Linux Manuals
NAME
dla_lin_berr.f 
SYNOPSIS
Functions/Subroutines
subroutine dla_lin_berr (N, NZ, NRHS, RES, AYB, BERR)
DLA_LIN_BERR computes a componentwise relative backward error.
Function/Subroutine Documentation
subroutine dla_lin_berr (integerN, integerNZ, integerNRHS, double precision, dimension( n, nrhs )RES, double precision, dimension( n, nrhs )AYB, double precision, dimension( nrhs )BERR)
DLA_LIN_BERR computes a componentwise relative backward error.
Purpose:

DLA_LIN_BERR computes componentwise relative backward error from the formula max(i) ( abs(R(i)) / ( abs(op(A_s))*abs(Y) + abs(B_s) )(i) ) where abs(Z) is the componentwise absolute value of the matrix or vector Z.
Parameters:

N
N is INTEGER The number of linear equations, i.e., the order of the matrix A. N >= 0.
NZNZ is INTEGER We add (NZ+1)*SLAMCH( 'Safe minimum' ) to R(i) in the numerator to guard against spuriously zero residuals. Default value is N.
NRHSNRHS is INTEGER The number of right hand sides, i.e., the number of columns of the matrices AYB, RES, and BERR. NRHS >= 0.
RESRES is DOUBLE PRECISION array, dimension (N,NRHS) The residual matrix, i.e., the matrix R in the relative backward error formula above.
AYBAYB is DOUBLE PRECISION array, dimension (N, NRHS) The denominator in the relative backward error formula above, i.e., the matrix abs(op(A_s))*abs(Y) + abs(B_s). The matrices A, Y, and B are from iterative refinement (see dla_gerfsx_extended.f).
BERRBERR is DOUBLE PRECISION array, dimension (NRHS) The componentwise relative backward error from the formula above.
Author:

Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
 September 2012
Definition at line 102 of file dla_lin_berr.f.
Author
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